For at least 20 years some of us have been trying patiently to explain why it is time to bury the so-called nature/nurture dichotomy as a hangover from an earlier phase of science. Attempts to partition out living processes into genetic and environmental misrepresents the way that living organisms construct themselves out of the raw materials provided by both genome and context. Development, from the fusion of sperm and egg through life's trajectory to maturity and the finality of death, cannot be decomposed in this way. Simple-minded claims that there are "genes for" this or that trait - even the most obvious, such as eye-colour - without understanding that how a gene is expressed depends both on the active cooperation of many other genes, and on the cell within which the genome is embedded, are misleading. Nor is "the environment" a simple concept, embracing as it does everything from the entirety of the cellular DNA via the organism as a whole, to the ever-changing physical and living worlds in which all life is embedded.

Making these points has led to much abuse. We have been accused of being naïve environmentalists, or even political ideologues, by polemicists on the other side of what have been called "the Darwin wars". Our "opponents", in turn, have rejected indignantly the charge that they might be genetic determinists or reductionists. The controversies have been fought out in wave after wave of popular books, whose sales have warmed the hearts of publishers and literary agents alike.

Now along comes Matt Ridley, a prolific and articulate campaigner in these battles, waving a flag of truce. Nature (genes), he announces, works by affecting nurture, while nurture (environment) affects how genes act. HOORAY, as Ridley would say (he is fond of launching into capitals to emphasise a point). Could sanity be breaking out at last? Well, yes and no. With Steven Pinker's The Blank Slate only recently published, and much quoted by Ridley, to be followed almost immediately by The Essential Difference (yet another skirmish in the sex war by Simon Baron-Cohen, also much cited by Ridley), it isn't quite clear who he sees as being in charge of negotiating terms for this peace.

But progress is being made and it would be churlish not to welcome it. The central issue is to understand the role played by the 30,000 or so genes we humans possess in the development of the hundred trillion cells of our bodies, and why it is that despite the tiny difference between the chimpanzee and the human genome, no one would mistake one of us for one of them. The key lies in development and, during development, the ordered way in which, at any one time, the cellular environment (itself, in part, the product of earlier gene action) switches on and off particular genes. The metabolic control processes that ensure this are vested in the cell system as a whole and, of course, are responsive to events in the environment outside the cell and the organism. You only have to think of the metabolic reorganisation demanded from the newborn baby as she emerges from the protection of the womb into the rough and tumble of the outside world, needing at once to engage previously untried mechanisms enabling her to breathe, to suckle, to regulate her temperature.

As with many professional science writers, Ridley's way of making these points is somewhat anecdotal, bringing his thesis to life by vignettes of particular researchers who have walk-on parts for half a page or so, never to appear again. He also has a habit - attractive to many of his readers, but irritating to me - of grabbing one metaphorically by the collar to spell out what he sees as the moral of his stories, some of which have by now become somewhat worn in the telling. But although his tales of how genes and environment mutually interact are largely accurate, he still has problems in recognising just how complex are the biological and behavioural issues. Thus he discusses research showing that a gene for a protein called CREB is activated when animals learn - but hasn't cottoned on to the fact that they can still learn without CREB providing one modifies the training routine. And he points rightly to the conflicting data on genes that might be relevant to schizophrenia, but doesn't take on board the claims by many psychiatrists that the very diagnostic category itself is insecure and that maybe it should be abandoned.

The Italians have a word for those who see the error of their past ways - pentiti - repentants. Matt Ridley is on the road, and it will be nothing but a pleasure to help him along it, but his pilgrimage is not quite over yet.

· The new edition of Steven Rose's The Making of Memory will be published this autumn.